How to deactivate User Persp (Local) view?
To go back to Global perspective view, go to View -> "View Global/Local". The hotkey is Numpad /. You probably pressed this when you accidentally switched to local view. This also works for otho view as well, from global to local and back. (Just to add it in, here's a YouTube video explaining how it can be used to un-clutter your scene for easier editing.)